Marinating chicken will add a few calories, but not many. Some marinades are high in sugar, and some contain oil. However, most of the marinade is going to drip off while cooking, leaving very little behind. The breading on fried chicken, however, will soak up the oil and keep it there.
I think I would ignore her adivce!
I'm in shock that Cracker Barrel has something which may pass as low fat, lol! I've never noticed anything grilled on their menu before, but I was probably too busy concentrating on the hash brown casserole